Regenerated collagen fiber with excellent heat resistance

ABSTRACT

A regenerated collagen fiber which comprises 100 parts by weight of collagen and 1 to 100 parts by weight of a thermoplastic resin and has such excellent heat resistance that it is less apt to be thermally damaged even in styling with a hair iron or dryer. The thermoplastic resin is one obtained by polymerizing at least one member selected from the group consisting of alkyl acrylate monomers, alkyl methacrylate monomers, acrylic acid, methacrylic acid, vinyl cyanide monomers, aromatic vinyl monomers and halogenated vinyl monomers.

RELATED APPLICATIONS

This application is a nationalization of PCT application PCT/JP00/04711filed Jul. 13, 2000. This application claims priority from the PCTapplication and Japan Application Serial No. Hei 11-200294 filed Jul.14, 1999.

TECHNICAL FIELD

This invention relates to a regenerated fiber. More particularly, itrelates to a regenerated collagen fiber with excellent heat resistance,which can suitably be used for human hair or fur, or as thread to bewound by hand.

BACKGROUND ART

Among the protein fibers, the regenerated collagen fiber exhibits a highmechanical strength like silk; and, thus, has been used in variousfields. Particularly, the regenerated collagen fiber is a protein fibermaintaining a characteristic molecular structure derived from collagenand, thus, is close in drape, luster and feel to the human hair that isa natural protein fiber having complex fine structure. Such being thecase, there have been attempts to use the regenerated collagen fiber asa replacement for human hair or in an animal hair-like fiber such as afur (for example, see Japanese Patent Laid-Open No. 168628/1998 andJapanese Patent Laid-Open No. 168629/1998).

In general, the skin or bone of an animal is used as a raw material forthe regenerated collagen fiber. The regenerated collagen fiber can beproduced by treating these raw materials with an alkali or an enzyme toobtain a water-soluble collagen, followed by extruding and spinning thewater-soluble collagen in an aqueous solution of an inorganic salt.Since the regenerated collagen fiber thus obtained is soluble in water,some treatments are applied thereto in order to impart resistance towater to the collagen fiber. As a method for making the regeneratedcollagen fiber insoluble in water, there are known methods includingtreating the water-soluble collagen fiber with an aldehyde compound suchas formaldehyde or glutaric aldehyde; treating the water-solublecollagen fiber with metal salts such as various chromium salts, aluminumsalts or zirconium salts; treating the water-soluble collagen fiber withan epoxy compound; and treating the regenerated collagen fiber with acombination of the above-described methods (for example, Japanese PatentLaid-Open No. 173161/1994).

However, being produced from collagen, the fiber produced by thesemethods has a lower heat resistance than that of human hair or animalhair containing keratin as a major component, and is susceptible tothermal damages (contraction in length, curling or hardening of hairtips) upon styling with a hair iron or dryer, thus rendering suchstyling unsatisfactory in view of its inherent properties (the term“styling” as used herein means to impart a desired form to human hair bythermal treatment in a beauty parlor or at home).

An object of the invention is to provide a regenerated collagen fiberwith excellent heat resistance, which is less apt to be damaged evenwhen styled with a hair iron or dryer.

SUMMARY OF THE INVENTION

Under such circumstances, as a result of intensive investigations, theinventors have found that the regenerated collagen fiber with excellentheat resistance can be obtained by compounding 1 to 100 parts by weightof a thermoplastic resin with 100 parts of collagen. Specifically, theinvention is embodied in a regenerated collagen fiber comprising 100parts by weight of collagen and 1 to 100 parts by weight of athermoplastic resin, with the thermoplastic resin preferably beingobtained by polymerizing at least one member selected from the groupconsisting of alkyl acrylate monomers, alkyl methacrylate monomers,acrylic acid, methacrylic acid, vinyl cyanide monomers, aromatic vinylmonomers, and halogenated vinyl monomers. The invention is also embodiedin a method of producing such a regenerated collagen fiber.

BEST MODE FOR CARRYING OUT THE INVENTION

As a raw material of collagen to be used in the invention, split leatheris preferred. The split leather can be obtained from a fresh raw hidesor salted hides of animals such as cows. Such split leather primarilycomprises insoluble collagen fibers, and is usually used after removingflesh portions attached thereto and a salt component used for preventingthe leather from becoming putrid or deteriorated.

Split leather in this condition still contains impurities; for example,lipids such as glyceride, phospholipid and free fatty acids, andproteins other than collagen, such as sugar proteins and albumin. Sincethese impurities greatly affect (adversely) the spinning stability informing fiber, the quality such as luster and elongation of theresultant fiber; and the odor, it is desirable to remove theseimpurities in advance. They may be removed, for example, by dippingsplit leather in lime to hydrolyze the fat components so as to loosenthe collagen fiber, followed by applying a conventional hide treatmentsuch as an acid-alkali treatment, an enzyme treatment and a solventtreatment.

The thus treated insoluble collagen is subjected to a solubilizingtreatment in order to cut the crosslinking peptide portion. As such asolubilizing treatment, there may be employed an alkali solubilizingmethod or an enzyme solubilizing method, each of which is commonlyemployed as a solubilizing treatment method.

In the case of employing the alkali solubilizng method, it is desirableto neutralize the solubilized collagen with an acid such as hydrochloricacid. It is also possible to employ the method described in JapanesePatent Publication No. 15033/71 as an improved alkali solubilizingmethod.

The use of an enzyme solubilizing method is advantageous in that it ispossible to obtain a regenerated collagen having a uniform molecularweight. Thus, an enzyme solubilizing method can be favorably employed inthe invention. As such an enzyme solubilizing method, the methodsdescribed in Japanese Patent Publication No. 25829/68 or Japanese PatentPublication No. 27513/68, for example, can be employed. Incidentally, itis possible in the invention to employ in combination both the alkalisolubilizing method and the enzyme solubilizing method.

Where additional treatments such as pH adjustment, salting-out, waterwash and treatment with a solvent are applied to the collagen after asolubilizing treatment has been applied, it is possible to obtain aregenerated collagen fiber having an excellent quality. Thus, it isdesirable to apply these additional treatments to the solubilizedcollagen.

The solubilized collagen leather pieces thus obtained are dissolved inan acidic aqueous solution having the pH value adjusted to 2 to 4.5 withhydrochloric acid, acetic acid, lactic acid or the like to provide astock solution of a predetermined concentration. For example, an aqueoussolution of about 1 to about 15% by weight, preferably about 2 to about10% by weight, of collagen is prepared.

According to the invention, a thermoplastic resin is added to eithersolubilized collagen leather pieces before the acid is added thereto, orto an aqueous solution of collagen to which the acid has been added. Ineither case, the resin is added in an amount of 1 to 100 parts by weightper 100 parts by weight of collagen.

The amount of the thermoplastic resin to be compounded is preferably 3to 80 parts by weight, and more preferably 5 to 50 parts by weight. Ifthe amount is less than 1 part by weight, the effect of improving heatresistance tends to become insufficient whereas, in case where there ismore than 100 parts by weight, the result tends to be a fragile fiberwhich is difficult to handle, though heat resistance is improved.

The mechanism by which heat resistance improved by compounding thethermoplastic resin is not clear, but it may be presumed thatthermoplastic resin particles existing inside the regenerated collagenfiber form some structure within the fiber which functions to inhibitdeformation such as contraction of collagen molecules upon heating witha hair iron or the like.

As the thermoplastic resin to be compounded, there may preferably beused those resins which are prepared by homopolymerizing orcopolymerizing two or more of the monomers such as alkyl acrylatemonomers (alkyl moiety containing preferably 1 to 12, more preferably 1to 6, carbon atoms) (e.g., methyl acrylate, ethyl acrylate, butylacrylate or octyl acrylate); alkyl methacrylate monomers (alkyl moietycontaining preferably 1 to 6, more preferably 1 to 4, carbon atoms)(e.g., methyl methacrylate or ethyl methacrylate); acrylic acid ormethacrylic acid; vinyl cyanide monomers (e.g., acrylonitrile ormethacrylonitrile); aromatic vinyl monomers (e.g., styrene ora-methylstyrene); and vinyl halide monomers (e.g., vinyl chloride orvinyl bromide). In addition to the monomers, crosslinking agents such asdivinylbenzene, monoethylene glycol dimethacrylate and polyethyleneglycol dimethacrylate may be used alone or as a mixture of two or more.Of these alkyl acrylate monomers, alkyl methacrylate monomers andaromatic vinyl monomers are preferred as the monomers for producing theresin to be compounded, with a combination of an alkyl acrylate monomerand an alkyl methacrylate monomer, and a combination of an alkylacrylate monomer and an aromatic vinyl monomer being more preferred. Inparticular, a combination of methyl methacrylate and butyl acrylate anda combination of styrene and butyl acrylate are preferred.

The thermoplastic resin has a glass transition temperature of 0° C. to120° C., preferably 30° C. to 100° C., and more preferably 30° C. to 80°C. The term “glass transition temperature” as used herein means a middleglass transition temperature of a peak measured at a temperature-raisingrate of 10° C./min according to the method described in JISK7121. In thecase where the glass transition temperature is less than 0° C., thethermoplastic resin particles are liable to agglomerate uponcompounding, leading to formation of large masses which reduce thestrength the of resultant regenerated collagen fiber containing them. Onthe other hand, in the case where the glass transition temperatureexceeds 120° C., effects obtained by compounding the thermoplastic resintend to be weakened.

Furthermore the thermoplastic resin particles have a particle size ofpreferably 5 μm or less, more preferably 1 μm or less, and still morepreferably 0.5 μm or less. In the case where the particle size exceeds 5μm, there tends to result a fragile fiber. For the thermoplastic resinparticles, powder pulverized with a mill or latex particles prepared byemulsion polymerization or suspension polymeriation may be used. Inparticular, latex particles obtained by emulsion polymerization areuniform in particle size and has a good stability in water. Therefore,they are easy to handle; thus being preferably used.

In compounding the thermoplastic resin particles with the solubilizedcollagen, an acid is further added after compounding the thermoplasticresin particles, followed by stirring the mixture well in a kneader orthe like for 2 hours or longer, preferably 5 hours or longer, to preparean aqueous solution of collagen wherein the particles are uniformlydispersed. In addition, in compounding the thermoplastic resin with anaqueous solution of collagen, the mixture is stirred well for 1 hour orlonger in a kneader or the like to uniformly disperse the thermoplasticresin particles in the aqueous solution of collagen. These proceduresare conducted at a temperature of preferably 25° C. or lower. In casewhere the temperature is higher than 25° C., the aqueous solution ofcollagen might be denatured, leading to difficulty in stable productionof fiber. Further, in the case of using a thermoplastic resin having aglass transition temperature of lower than 25° C., it is desirable toconduct the treatment at a temperature no higher than the glasstransition temperature of the added resin in order to preventagglomeration of the resin particles.

Additionally, the thus obtained aqueous solution of collagen may, ifnecessary, be subjected to a defoaming procedure by stirring underreduced pressure, or to a filtering procedure, to remove large-sizedforeign matter.

Further, to the thus obtained aqueous solution of the solubilizedcollagen may, if necessary, be added additives such as a stabilizer anda water-soluble high-molecular compound in proper amounts. The purposeof this, for example, is improving mechanical strength, resistance towater and to heat, luster and spinning properties, preventing colorationand imparting antiseptic properties.

The aforesaid aqueous solution of the solubilized collagen is thendischarged through, for example, a spinning nozzle or slit. Thedischarged solution is dipped in an aqueous solution of an inorganicsalt so as to obtain a regenerated collagen fiber. As the aqueoussolution of an inorganic salt, an aqueous solution of a water-solubleinorganic salt such as sodium sulfate, sodium chloride or ammoniumsulfate. Usually, the inorganic salt concentration in the aqueoussolution is adjusted to 10 to 40% by weight.

PH of the aqueous solution of the inorganic salt is desirably adjustedto 2 to 13, preferably 4 to 12, by adding a metal salt such as sodiumborate or sodium acetate or hydrochloric acid, acetic acid or sodiumhydroxide to the aqueous solution. In case where the pH value is smallerthan 2 or exceeds 13, the peptide linkage of collagen is likely to behydrolyzed, sometimes resulting in failure to obtain a desired fiber.

Also, it is desirable for the temperature of the aqueous solution of theinorganic salt, which is not particularly limited in the presentinvention, to be adjusted in general, for example, to 35° C. or lower.In case where the temperature of the aqueous solution is higher than 35°C., the soluble collagen is denatured or the mechanical strength of thespun fiber is lowered, with the result that it becomes difficult tomanufacture fiber thread with a high stability. The lower limit of thetemperature range is not particularly limited in the invention. Itsuffices to adjust the lower limit of the temperature appropriately inaccordance with the solubility of the inorganic salt.

Then, these fibers are commonly treated with a crosslinking agent forimproving resistance to water. As methods for treating with acrosslinking agent, there are illustrated, for example, a method ofpreviously adding a crosslinking agent to the aqueous solution of aninorganic salt, and conducting the water resistance-imparting-treatmentsimultaneously with spinning, and a method of subjecting a spunregenerated collagen fiber to a treatment with a crosslinking agent.

As the crosslinking agent, there are illustrated, for example,monoaldehydes such as formaldehyde, acetaldehyde, methyl glyoxal,acrolein, and crotonaldehyde; dialdehydes such as glyoxal,malondialdehyde, succindialdehyde, glutaraldehyde, and dialdehydestarch; alkylene oxides such as ethylene oxide and propylene oxide;halogenated alkylene oxides such as epichlorohydrin; epoxy compoundsincluding glycidyl ethers of aliphatic alcohol, glycol and polyols, andglycidyl esters of monocarboxylic acid, dicarboxylic acid, andpolycarboxylic acid; N-methylol compounds derived from urea, melanin,acrylamide acrylic acid amide and polymers thereof; water solublepolyurethanes prepared by introducing isocyanate into a polyol or apolycarboxylic acid, followed by adding sodium hydrogen sulfite;triazine derivatives such as monochlorotriazine and dichlorotriazine;sulfate ester of oxyethyl sulfone or derivatives of vinyl sulfone;trichloropyridine derivatives; dichloroquinoxaline derivatives;N-methylol derivatives; isocyanate compounds; phenol derivatives;aromatic compounds having a hydroxyl group represented by tannin; andinorganic crosslinking agents of metal salts wherein a cation of metalsuch as aluminum, chromium, titanium or zirconium is combined with ananion such as sulfate ion, nitrate ion, halide ion represented bychloride ion or hydroxyl ion. However, the crosslinking agents to beused in the invention are not limited only to these. Other crosslinkingagents may also be used which can reduce contraction with hot water,water absorption or swelling degree in water of the regenerated collagenand can make the regenerated collagen fiber insoluble in water.Additionally, water-insoluble crosslinking agents may be used as anemulsion or a suspension. These crosslinking agents may usually be usedalone or as a mixture of two or more of them.

Of these crosslinking agents, metal salts can impart a particularlyexcellent heat resistance to the regenerated collagen. In particular,use of an aluminum salt realizes remarkable effects by the addition ofthe thermoplastic resin, thus being particularly preferred in theinvention.

Further, in the invention, water wash, oiling and drying are applied asrequired to the regenerated collagen fiber.

Drying is usually conducted in a hot air convection dryer. Theregenerated collagen fiber is liable to contract upon being dried, andit is extremely difficult for the once deformed collagen fiber to beformed into a desired form. Thus, in the invention, drying is conductedin a state wherein the fiber is fixed at both ends under tension or in astretched state wherein a load is applied to both ends of the fiber sothat the contraction ratio of the fiber after drying becomes 30% orless, preferably 20% or less, and still more preferably 10% or lesswithout being broken. In case where the contraction ratio of the fiberthread after drying exceeds 30%, complicated unevenness tends to beformed on the surface of the fiber to cause detrimental influences ontouch feel. The atmospheric temperature within the dryer is notparticularly limited, but a temperature of not lower than the glasstransition temperature of the added thermoplastic resin is preferredbecause the effect of improving heat resistance is more remarkable. Thismay be attributed to a continuous structure being formed within theregenerated collagen fiber by welding of the added thermoplastic resinparticles to each other, which serves to improve heat resistance.Further, as to the atmospheric temperature within the dryer, it ispreferably 100° C. or lower, and more preferably 90° C. or lower;because, in case where it is too high, the fiber might be colored ordenatured. Drying lime is longer than that which is required tocompletely dry the fiber and shorter than that at which decoloration ofthe fiber becomes serious.

The water wash is intended to prevent precipitation of an oiling agentcaused by a salt and to prevent the salt from being precipitated fromthe regenerated collagen fiber during drying within a drying machine. Inthe case where the salt is precipitated, the regenerated collagen fiberis cut or broken, and the formed salt scatters within the drying machineso as to be attached to the heat exchanger within the drying machine,leading to a low heat transfer coefficient. Also, the oiling iseffective for preventing the fiber from hanging up in the drying stepand for improving the surface state of the regenerated collagen fiber.

The thus obtained regenerated collagen fiber containing thethermoplastic resin has an excellent heat resistance, and enablesstyling with a hair iron or dryer to be conducted with the drape that anatural protein fiber has, being maintained. The fiber is, accordingly,more favorably usable as a substitute or a piece for improving humanhair and animal hair.

The invention is now described in more detail by reference to Examples.However, the examples do not limit the invention in any way.

Additionally, in the invention, heat resistance of the regeneratedcollagen fiber is evaluated by measuring contraction ratio of the fiberand damage of the fiber at its tip upon applying thereto a hair iron,with these being taken as representative data for heat resistance.Fineness of the fiber is represented in terms of d (denier) and dtex(decitex).

Glass transition temperature and particle size of the thermoplasticresin used in Examples and heat resistance of the regenerated collagenfiber prepared in Examples upon applying a hair iron were measuredaccording to the following methods.

(1) Glass Transition Temperature of the Thermoplastic Resin Particles

A thermoplastic resin latex obtained by emulsion polymerization wasdried at 25° C. for 48 hours, then kept in a 25° C. vacuum dryer for 24hours to obtain powder from which moisture was completely removed. About10 mg of the powder was taken out according to the method described inJISK7121, and a middle-point glass transition temperature of the peakwas read off, the peak being measured using differential scanningcalorimeter (made by Seiko Denshi Kogyo K. K.; DSC-220C) under theconditions of −50° C. in initial temperature and 10° C./min intemperature-raising rate.

(2) Particle Size of the Thermoplastic Resin Particles

A thermoplastic resin latex obtained by emulsion polymerization wasdried at 25° C. for 48 hours to obtain powder, and this powder wasobserved using a scanning type electron microscope (made by Hitachi,Ltd.; S-800) to measure the particle size.

(3) Heat Resistance Upon Applying a Hair Iron

The following procedures were conducted in an atmosphere of 20±2° C. intemperature and 65±2% in relative humidity.

After well opening the fibers, they were bunched in a length of 250 mm.To the bunch of fibers was lightly applied a hair iron (Perming Iron;made by Hakko Kogyo K. K.) heated to a varying temperature, and the hairiron was slid once rapidly (2 sec/slide) along the upper surface and thelower surface to evaporate moisture on the surface of the fibers. Then,the bunch of fibers was nipped with the iron, and the iron was slid fromthe base to the top of the bunch of fibers in 5 seconds. After thisprocedure, contraction ratio of the fiber bunch and the shrank state ofthe fiber at its tip were examined. Contraction ratio was determinedfrom the following formula [1]

Contraction ratio=[(L−Lo)/L]×100  [1]

wherein L represents a length of the fiber bunch before being treatedwith the iron, and Lo represents a length of the fiber bunch after beingtreated with the iron (in case where wave is formed in the fiber bunchupon treating with the iron, the length being measured by straighteningthe fiber bunch).

Hair iron heat resistance was described in terms of a hair ironheat-resistant temperature which was measured as the maximum temperatureat which contraction ratio was 5% or less and no shrinkage was observed.The hair iron temperature was raised by 10° C., and the fiber bunch waschanged to a new fiber bunch upon measuring at each differenttemperature.

EXAMPLE 1

Emulsion polymerization was conducted using 60 parts by weight ofstyrene, 40 parts by weight of butyl acrylate, and 1 part by weight of asurfactant of sodium laurylsulfate to obtain a latex containing 20% byweight of a solid component comprising resin particles having a glasstransition temperature of 41° C. and a particle size of 0.1 μm. Further,45 g of the latex (resin: 9 g) was mixed with 1200 g (collagen content:180 g) of leather pieced obtained by solubilizing split leather with analkali. Then, an aqueous solution of lactic acid and water were addedthereto in a definite amount, and the mixture was stirred in a kneader(made by K. K. Irie Shokai; Model PNV-5; hereinafter the same) toprepare a stock solution having a pH adjusted to 3.5 and a solidcomponent (comprising collagen and the thermoplastic resin)concentration adjusted to 7.5% by weight. Thereafter, the solution wassubjected to a defoaming treatment by stirring under a reduced pressure(using a stirring defoamer, model 8DMV, made by Dalton Corporation) forone hour, followed by transferring the treated solution to a piston typespinning stock solution tank. The solution thus transferred was furtherallowed to stand under a reduced pressure to defoam. Then, the stocksolution was extruded by a piston, followed by transferring apredetermined amount of the extruded solution by a gear pump andsubsequently filtering the extruded solution through a sintered filterof 10 μm in pore size. Further, the filtered extrudate was passedthrough a spinning nozzle having 300 pores each pore having a porediameter of 0.30 mm and a pore length of 0.5 mm so as to discharge thefiltered extrudate at a spinning rate of 5 m/min into a coagulating bathof 25° C. in temperature containing 20% by weight of sodium sulfate andhaving the pH value adjusted to 11 with boric acid and sodium hydroxide.

Then, the resultant regenerated collagen fiber was dipped in 16.5 kg ofan aqueous solution containing 1.7% by weight of epichlorohydrin, 0.09%by weight of 2,4,6-tris(dimethylaminomethyl)phenol, 0.009% by weight ofsalicylic acid and 13% by weight of sodium sulfate at 25° C. for 24hours.

After washing the resultant collagen fiber with a flowing water for onehour, it was dipped in 16.5 kg of an aqueous solution containing 6% byweight of basic aluminum chloride (made by Nihon Seika K. K.; Bercotan AC-P; hereinafter the same) and 5% by weight of sodium chloride at 30° C.for 12 hours, followed by washing the resultant fiber with a flowingwater for 2 hours.

Subsequently, the fiber was dipped in a bath filled with an oily agentconsisting of an emulsion of an amino-modified silicone and PLURONICpolyether antistatic agent so as to allow the oily agent to adhere tothe fiber, then dried under tension in a hot air convection dryer (TABAIESPEC CORP; PV-221; hereinafter the same) whose temperature was set to60° C. with fixing one end of the fiber bunch and applying a load of0.04 g per d (1.1 dtex). As a result of measuring iron heat resistance,the hair iron heat resistance temperature was measured to be 160° C.

EXAMPLE 2

The same procedures as in Example 1 were conducted except for changingthe amount of latex to 90 g (resin: 18 g). As a result of measuring ironheat resistance, the hair iron heat resistance temperature was measuredto be 170° C.

EXAMPLE 3

The same procedures as in Example 1 were conducted except for changingthe amount of latex to 270 g (resin: 54 g). As a result of measuringiron heat resistance, the hair iron heat resistance temperature wasmeasured to be 180° C.

EXAMPLE 4

Emulsion polymerization was conducted using 80 parts by weight of methylmethacrylate, 20 parts by weight of butyl acrylate, and 1 part by weightof a surfactant of sodium laurylsulfate to obtain a latex containing 20%by weight of a solid component comprising resin particles having a glasstransition temperature of 73° C. and a particle size of 0.1 μm.

90 g of the latex (resin: 18 g) was mixed with 1200 g (collagen content:180 g) of leather pieces obtained by solubilizing split leather of acattle with an alkali. Subsequent procedures were conducted in the samemanner as in Example 1 except for changing the temperature of the hotair convection drying machine to 85° C. As a result of measuring ironheat resistance, the hair iron heat resistance temperature was measuredto be 160° C.

EXAMPLE 5

The same procedures as in Example 4 were conducted except for changingthe amount of latex to 180 g (resin: 36 g). As a result of measuringiron heat resistance, the hair iron heat resistance temperature wasmeasured to be 170° C.

EXAMPLE 6

The same procedures as in Example 5 were conducted except for changingthe temperature of the hot air conviction drying machine to 60° C. As aresult of measuring iron heat resistance, the hair iron heat resistancetemperature was measured to be 160° C.

EXAMPLE 7

The same procedures as in Example 2 were conducted except for conductingthe insolubilizing treatment by dipping the regenerated collagen fiberin a 25° C. aqueous solution containing 15% by weight of sodium sulfateand 0.5% by weight of formaldehyde (pH being adjusted to 9 with boricacid and sodium hydroxide) for 15 minutes in place of the treatment withepichlorohydrin. As a result of measuring iron heat resistance, the hairiron heat resistance temperature was measured to be 180° C.

COMPARATIVE EXAMPLE 1

The same procedures as in Example 1 were conducted except for not mixingthe latex. As a result of measuring iron heat resistance, the hair ironheat resistance temperature was measured to be 140° C., which is lowerthan that obtained by adding the thermoplastic resin and subjecting tothe same crosslinking method.

COMPARATIVE EXAMPLE 2

The same procedures as in Example 1 were conducted except for changingthe amount of latex to 1350 g (resin: 270 g). The resultant regeneratedcollagen fiber was so fragile that it suffered fiber breakage upondrying and not being taken out as thread.

COMPARATIVE EXAMPLE 3

The same procedures as in Example 7 were conducted except for not mixingthe latex. As a result of measuring iron heat resistance, the hair ironheat resistance temperature was measured to be 160° C., which is lowerthan that obtained by adding the thermoplastic resin and subjecting tothe same crosslinking method.

Data obtained in Examples and Comparative Examples are shown in Table 1.

TABLE 1 Compounded Thermoplastic Resin Glass Amount Per RegeneratedCollagen Fiber Formulation Transition Particle 100 Parts of Drying HairIron Heat Resistant (parts by Temperature Size Collagen (partsCrosslinking Temperature Temperature weight) (° C.) (μm) by weight)Method (° C.) (° C.) Example 1 ST 60 41 0.1  5 ECH/AL 60 160 BA 40 2 ST60 ″ ″ 10 ″ ″ 170 BA 40 3 ST 60 ″ ″ 30 ″ ″ 180 BA 40 4 MMA 80 73 ″ 10 ″85 160 BA 20 5 MMA 80 ″ ″ 20 ″ ″ 170 BA 20 6 MMA 80 ″ ″ 20 ″ 60 160 BA20 7 ST 60 41 ″ 10 FA/AL ″ 180 BA 40 Comp. Ex. 1 — — — — ECH/AL ″ 140 2ST 60 41 0.1 150  ″ ″ Measurement being BA 40 impossible due to seriousfiber breakage 3 — — — — FA/AL ″ 160 Formulation of added resin: ST:styrene; BA: butyl acrylate; MMA; Methyl methacrylate; Method ofcrosslinking the regenerated collagen fiber: ECH: eipchlorohydrin; FA:formaldehyde AL: Basic aluminum chloride

It is seen from the results that heat resistance of the regeneratedcollagen fiber can be improved by incorporating the thermoplastic resin.

INDUSTRIAL APPLICABILITY

The invention is embodied in a method for improving heat resistance ofthe regenerated collagen fiber, which makes the regenerated collagenfiber into an extremely excellent product to be used as a substitute ofhuman hair, for example, wig or hair piece, or head-decorating productssuch as doll hair. It is also embodied in a heat resistant regeneratedcollagen fiber.

What is claimed is:
 1. A regenerated collagen fiber, comprising: 100parts by weight of a regenerated collagen; and 1 to 100 parts by weightof a thermoplastic resin compounded with said regenerated collagen,wherein the thermoplastic resin is one obtained by polymerizing at leastone member selected from the group consisting of alkyl acrylatemonomers, alkyl methacrylate monomers, acrylic acid, methacrylic acid,vinyl cyanide monomer, aromatic vinyl monomers and halogenated vinylmonomers.
 2. The regenerated collagen fiber as descried in claim 1,wherein the thermoplastic resin has a glass transition temperature of 0°C. to 120° C.
 3. The regenerated collagen fiber as described in claim 1,wherein the thermoplastic resin has a glass transition temperature of30° C. to 100° C.
 4. The regenerated collagen fiber as described inclaim 1, wherein the compound contains 3 to 80 parts by weight of thethermoplastic resin.
 5. The regenerated collagen fiber as described inclaim 1, wherein the compound contains 5 to 50 parts by weight of thethermoplastic resin.
 6. The regenerated collagen fiber, as described inclaim 1, wherein the resin comprises resin particles each having a sizeof 5 μm or less.
 7. The regenerated collagen fiber as described in claim1, wherein the fiber is formed by spinning.